One important way of making electronic equipment easier to use is to make operation of the equipment's user interface more intuitive. To this end, many electronic devices have graphical and/or menu-driven user interfaces. In those user interfaces options are displayed on a screen and can be scanned through or selected on the basis of the movement of a pointer. The pointer may be a cursor which is displayed, or may be a virtual pointer which is not displayed but can be considered by a user to be conceptually linked to the operation of the display (for example in the scrolling of a menu list). Input means is then provided for detecting inputs from a user that can cause movement of the pointer. Such input means preferably detect physical movement of part of the user's body, whereupon the pointer can be caused to move in a corresponding way. A number of types of such input means are currently preferred. For detecting motion in one dimension there are rotatable wheels or rollers linked to rotation sensors. For detecting motion in two dimensions there are mice and trackballs including multiple rotation sensors, trackpoints having multiple force sensors, joysticks having multiple sensors for detecting angular deflection, and touchpads which can determine the location of a pressure source such as a fingertip within the boundaries of the touchpad and over time establish the motion of the pressure source within those boundaries. An array of buttons or keys, suitably marked with direction arrows, can also be used.
These forms of motion detection all have disadvantages, especially for highly portable equipment such as mobile telephones. Where equipment is intended to be highly portable it is greatly desirable that it is small and light-weight and, to improve reliability, that it has no moving parts. Wheels, rollers, trackballs, mice and joysticks must be large enough to be conveniently engaged by a user's hand and have moving parts and rotation or other detectors that are easily disrupted by dirt that can accumulate during use. Dirt is a particular risk for items such as mobile telephones that are carried continually and often exposed to dusty or dirty environments. Trackpoints are highly compact but are difficult for some users to operate because the user's finger engaged on the trackpoint does not change position significantly during use. Touchpads can be found to be easier to operate because the user's finger must move across the surface of the touchpad in order to provide an input. Touchpads have therefore become popular for large-sized items of portable equipment such as laptop computers. However, touchpads are generally unsuitable for smaller devices such as modern mobile telephones because of the space needed to provide room on the touchpad for a finger to be able to be moved within its boundaries. With a touchpad, sensed movement is dependant principally on the location of pressure on the pad. Buttons and keys occupy a relatively large amount of space on a device and are less intuitive for users to operate than are other more tactile input means. Also, joysticks, mice, rollers and rollerballs are not capable of conveniently sensing rotating motion.
There is therefore a need for an improved means for control of user interfaces.